Discharge reaction

At the cathode, or positive electrode, lead dioxide [1309-60-0] Pb02, reacts with sulfuric acid to form lead sulfate [7446-14-2] PbSO, and water in the discharging reaction... 

Self-Discharge Processes. The shelf life of the lead—acid battery is limited by self-discharge reactions, first reported in 1882 (46), which proceed slowly at room temperature. High temperatures reduce shelf life significantly. The reactions which can occur are well defined (47) and self-discharge rates in lead—acid batteries having immobilized electrolyte (48) and limited acid volumes (49) have been measured. 

PIa.tes, Plates are the part of the cell that ultimately become the battery electrodes. The plates consist of an electrically conductive grid pasted with a lead oxide—lead sulfate paste which is the precursor to the electrode active materials which participate in the electrochemical charge—discharge reactions. 

Dynamic Ejfects Design must provide for impact (hydraulic shock, etc.), wind (exposed piping), earthquake (see ANSI A58.1), discharge reactions, and vibrations (of piping arrangement and support). 

Fig. 20.24 Potential energy-distance from metal surface curves, illustrating (a) an M /M system in which, owing to the relative position of the energy wells, the initial ionisation reaction occurs more rapidly than the discharge reaction, resulting in an excess negative charge on the surface of the metal, (b) equilibrium at which the energy wells are approximately the same and...

Figure 15. Reaction mechanism of the charging-discharging reaction of an MH electrode.

Oxygen evolution occurs on nickel oxide electrodes throughout charge, on overcharge, and on standby. It is the anodic process in the self-discharge reaction of the positive electrode in nickel-cadmium cells. Early work in the field has been reviewed [9], No significant new work has been reported in recent years. 

In the lead-acid battery, sulfuric acid has to be considered as an additional component of the charge-discharge reactions. Its equilibrium constant influences the solubility of Pb2+ and so the potential of the positive and negative electrodes. Furthermore, basic sulfates exist as intermediate products in the pH range where Fig. 1 shows only PbO (cf. corresponding Pour-baix diagrams in Ref. [5], p. 37, or in Ref. [11] the latter is cited in Ref. [8]). Table 2 shows the various compounds. 

The charge-discharge reaction of the negative electrode corresponds to curve A in Fig. 1, but the Pb2+ ion activity is now determined by the solubility of lead sulfate (PbS04). Thus Eq. (12) has to be modified into... 

Figure 2. Reactions that occur in lead-acid batteries versus electrode potential (thermodynamic situation). Their equilibrium potentials are inserted as boxed numbers. Equilibrium potentials of the charge-discharge reactions (Pb/PbS04 and PhS04/Pb02) are represented by hatched columns, to indicate their dependence on acid concentration. The inserted equilibrium potentials (-0.32 and +l. 75 V) of the charge discharge reactions correspond to an acid density of 1.23 gem 3.

Oxygen evolution according to Eq. (5) is possible above 1.23 V and forms the couple with the discharge reaction (the reversal of Eq.(21)) ... 

The charge-discharge reactions occur at the phase boundary between the active material and the electrolyte. To make sure that a sufficient rate of reaction is achieved, the surface of the reacting materials has to be large. Otherwise, the kinetic parameters would reduce the reaction rate too much. Table 5 shows the surface areas of the active materials in the positive and the negative electrode. 

Twice the amount of electricity is required compared with the discharge reaction at the negative electrode according to Eq. (18), since corrosion involves four valences, which means AF = 107.21 Ah per multiple of Eq. (31). Consequently, for the corrosion reaction according to Eq. (31) the equivalent values are ... 

Aluminum is directly applied in its metallic form when it serves as battery anode. The battery concepts considered are in general single-use types (primary batteries). The most developed systems belong to the metal-air batteries, using the reduction of atmospheric oxygen as the cathode reaction, e.g., (-) A1 / KOH / 02 (+) or (-) A1 / seawater / 02 (+). The main discharge reactions are ... 

The discharge reactions now include formation of hydroxo complexes, preferably ... 

In competition with the electrochemical discharge reaction and consequently di-... 

The solubility of nickel chloride in the molten electrolyte is of interest because high solubilities of nickel chloride will cause capacity loss over the lifetime. Dissolved nickel chloride will not be contacted by the electronically conductive backbone nickel and cannot participate in the discharge reaction. Therefore it is essential that the nickel chloride is formed... 

However, under these conditions, the energy density is lower than with the (CH> ), electrode, whereas, on the other hand, the coulombic efficiencies attain values of 98 %. In some cases PA in its n-doped form has also been used as battery anode (cell type 3) 190,191,241) -j-jjg discharging reaction in a cell with a TiS2 cathode is as follows ... 

There have been several reports of all-plastic batteries with PA-electrodes (cell type 4) -249,2S2,253) observcd cell potentials lie between 3.4 and 2.5 V, the short circuit current was 50 mA cm down to 12 mA cm . The overall discharge reaction is ... 

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